title: Autophagy stimulates apoptosis in HER2-overexpressing breast cancers treated by lapatinib.
abstract: HER2-overexpressing breast cancers often show hyperactivation of the HER2/AKT/mTOR signaling pathway. Lapatinib is an oral dual tyrosine kinase inhibitor (TKI) that targets both EGFR and HER2 to inhibit the proliferation of breast cancer cells. However, it is obscure whether and how lapatinib could induce autophagy in breast cancer cells, an important cell response with drug treatment. In this study, we investigated the apoptosis and the autophagy in the HER2-overexpressing breast cancer cells BT474 and AU565 treated with lapatinib, and further examined their relationship. Lapatinib inhibited the proliferation and the rate of DNA synthesis in HER2-positive cells, as observed by MTT, colony formation and EDU assays. Lapatinib not only induced apoptosis accompanied by an increased expression of cleaved Caspase-3 and cleaved PARP, but it also induced autophagy in vitro, as confirmed by electron microscopy (EM), acridine orange (AO) staining and LC3-II expression. Meanwhile, lapatinib inhibited the phosphorylation of HER2, AKT, mTOR, and p70S6K, whereas that of AMPK was activated. When the cells were pre-incubated with 3-Methyladenine (3-MA), the specific autophagy inhibitor, the growth inhibitory ratio and apoptosis rate were frustrated, whereas colony formation and DNA synthesis ability were encouraged. In addition, 3-MA application could up-regulate Caspase-3 and PARP expression, compared with the treatment with lapatinib alone. The addition of 3-MA could attenuate the inhibitory role on HER2/AKT/mTOR pathway and the active role on AMPK that was raised by lapatinib. Therefore, lapatinib simultaneously induced both apoptosis and autophagy in the BT474 and AU565 cells, and in these settings, autophagy facilitates apoptosis.
authors.affiliation: Department of Pharmaceutical Chemistry, The Fourth Military Medical University, Xi'an, Shaanxi, 710032, China.
authors.forename: Xingmei
authors.initials: X
authors.lastname: Zhu
authors.forename: Lin
authors.initials: L
authors.lastname: Wu
authors.forename: Hongyu
authors.initials: H
authors.lastname: Qiao
authors.forename: Tenglong
authors.initials: T
authors.lastname: Han
authors.forename: Suning
authors.initials: S
authors.lastname: Chen
authors.forename: Xueying
authors.initials: X
authors.lastname: Liu
authors.forename: Ru
authors.initials: R
authors.lastname: Jiang
authors.forename: Yifang
authors.initials: Y
authors.lastname: Wei
authors.forename: Dayun
authors.initials: D
authors.lastname: Feng
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yongzheng
authors.initials: Y
authors.lastname: Ma
authors.forename: Shengyong
authors.initials: S
authors.lastname: Zhang
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000225:Adenine / Q000008:administration & dosage / Q000031:analogs & derivatives; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D000077341:Lapatinib; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011799:Quinazolines / Q000008:administration & dosage*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000225:Adenine; D000077341:Lapatinib; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D018719:Erb-b2 Receptor Tyrosine Kinases; C025946:3-methyladenine; C508053:ERBB2 protein, human
keywords: AMPK; APOPTOSIS; AUTOPHAGY; BREAST CANCER; LAPATINIB; mTOR